Method of forming packing rings



Patented Apr. 13, 1937 UNi'lE STATES PATENT oFFIcE N0 Drawing. Original application April 8, 1935, Serial No. 15,353. Divided and this application October 9, 1935, Serial No. 44,231

4 Claims.

This invention relates to production of packing rings of the type employed for withstanding the high pressures occurring in hydraulic presses and for other similar uses where U-leather packings are commonly made use of. This application for patent is a division of a copending application for patent, Serial No. 15,353, Forming packing ring stock, filed April 8, 1935, Patent No. 2,053,363, of September 8, 1936 and relating to machines for the production of packings according to the method now claimed.

An object of the invention is to provide a method enabling the production of packings of improved quality of standard U-form and also the production of packings of special form which cannot be perfectly made by prior known methods.

A further object of the invention is to provide a method of producing ring packings whereby in the process the leather is stretched and conditioned in a manner favorable to the quality of the resulting article. Other objects of the invention are to avoid inherent difficulties in customary methods of producing packings, which difficulties are mainly the stretching of the leather in is a division, discloses a machine arranged for operating upon long strips of leather made up by connecting together the ends of comparatively short leather strips, lapped, cemented joints being employed.

The strips of stock operated upon are sometimes laminated and may include other fibrous material than leather, but the process is mainly intended for use in connection with natural leather of equal or less thickness than the normal hides from which it is formed.

The machine referred to performs a drawing process on strips of wax-loaded leather, while the temperature of the material operated upon is sufficient to keep the material soft and pliable. The drawing process is preferably performed by attaching the end of the leather strip to a mandrel upon which the leather is wound after it is formed into U, L or other cross section by passing through heated forming dies, one of which may surround the mandrel and have an internal forming thread. The equipment for performing the process may vary but the essential steps of the process are to heat and draw the wax-loaded strips through dies, form the strips into helices, or rings, and to hold them in that form While the product is chilled and set.

Further steps in the process are to make the finished rings of the desired diameter by ex-, panding them to the exact required diameters and joining the cut ends thereof by flush lapped cemented joints.

By means of this method here generally outlined, it is possible to avoid expensive and some: what defective methods now employed for forming U-shaped packing rings.

It has been common practice, in order to supply the customers requirements for U-packingsl intended for high pressure operation in hydraulic presses, to make use of steel forming rings, three of which are required for each diameter of U- packing ring. The trade requirements call for slight variations in diameter and even though the packing ring manufacturer may have an exceedingly large stock of expensive forming rings, there is always the necessity to provide new ones to take care of some odd cylinder bore or plunger diameters. The stock operated upon is in the form of leather discs requiring the use of more leather than actually goes into the finished packing, and that ring process of forming is decidedly limited as to the cross sections which may be formed.

The old process is exceedingly difiicult or useless in making rings of L-cross section, and has the decided disadvantage of drawing the leather in the wrong direction, with the likelihood of its crawling on the rings and also weakening the leather at the bends therein.

With the improved process the leather is drawn into form without injury or waste, and the fibres thereof are stressed in the right direction prior to chilling.

Prior methods, wherein the leather stock operated upon is first soaked in water and then rolled to form, have the disadvantage of shrinkage upon drying, and lack uniformity in thickness of the packing.

The present method of drawing the leather after it has been loaded with wax is an ironing out process which insures uniformity in thickness and other dimensions of the finished product.

Explaining the process more in detail, the material operated upon is in the form of leather belting filled with Wax. Sometimes the belt-like strips are laminated and all of the laminations do not extend from side to side thereof, as it is frequently desirable in the case of a U-packing to have one Wall of the U thicker than the other,

or to have the base of the U of greater thickness than the side walls. The belt-like strips are heated as they enter the forming dies through which the strips are drawn to gradually change their form into U, L, V, or other cross section. The final forming die is preferably adjacent the winding mandrel so as to guide the formed strips onto the mandrel upon which the strip is wound in a helix. In case the packing is of U form or similar thereto, it is necessary to feed into the leather strip a flexible filler or spacer strip between the arms of the U to keep the leather of the desired ultimate channel shape during the chilling operation. The chilling step is performed after the completion of the forming operation, while the leather helix is still on the mandrel, with the spacer strip still in place.

The spacer strip is flexible but of greater density in tensile strength than leather packing and is preferably cut to the desired dimensions from fabricated rubberized belting now on the market under various trade names and which is formed from numerous layers of finely woven duck or sheeting, rubber vulcanized under pressure to insure the required density.

I claim:

1. The method of forming ring packings of substantially U-cross section which consists in drawing wax treated strips of leather into channel form while applying heat and pressure thereto, and rolling such channel formed strips with a spacer between the legs of the same into a helix while the strip is heated.

2. The method of forming ring packings of substantially U-cross section which consists in drawing wax-treated strips of leather into channel form while applying heat and pressure thereto, and rolling such channel-formed strips with a spacer between the legs of the same into a helix while the strip is heated, and then chilling the helix.

3. The herein described method of manufacturing packing ring stock which consists in drawing wax-treated strips of leather through forming dies while applying heat and pressure thereto and thereby bending the strips longitudinally, then rolling such bent strips into a helix while the bent form is maintained, and then chilling the helix.

4. The method of forming packing rings which consists in superimposing and cementing together strips of leather of varying widths, drawing the laminated strips through creasing dies while applying heat thereto, and then winding the creased strips into helical form, and then chilling and cementing the formed helices.

WAYNE DAVIES. 

